Gaseous reservoir and method



Dec. 29, 1959 S. GOLDBERG ET AL GASEOUS RESERVOIR AND METHOD Filed Feb. 10, 1958 M mm AM HY mw R E $MN KKK a 0000 O OOO l l m B M w l5 T H 001 l O l T 1 O D 0 l 5 4 3 2 W 0 mmammwmu zo; 6omw o 225358 SE89 Q V wmawwwmu INVENTORS SEYMOUR GOLDBERG EDWARD J. GOON ATOMIC RATIO OF GAS ABSORBED IN RESERVOIR WNW ' ATTORNEYS United States Patent GASEOUS RESERVOIR AND METHOD Seymour Goldberg, Lexington, and Edward J. Goon,

Burlington, Mass., assignors to Edgerton, Ger-meshausen and Grier, Inc., Boston, Mass., a corporation of Massachusetts Application February 10, 1958, Serial No. 714,086

Claims. (Cl. 313-178) The present invention relates to gaseous-discharge devices and the like and, more particularly, to reservoirs for supplying gas in such devices.

When gaseous-discharge devices, such as, for example, rectifiers and thyratrons, are operated, appreciable pressure fluctuations occur during the initial instants of operation. Pressure variations also occur during subsequent life-time operation of such devices. The processes involved in such variations, including variations caused by so-called cleanup phenomena, are imperfectly understood at present so that resort has been had to the use of pressure-equalizing reservoirs of gas within the gaseous-discharge device. Ideally, by supplying additional gas to the device to replace cleanup losses, the reservoirs should maintain a constant equilibrium pressure in the tube. Heretofore, an approximation only to such an ideal has been obtained by employing, for example, a heated titanium or zirconium reservoir containing occluded or absorbed hydrogen gas. Unfortunately, however, the characteristics of these materials are such that, at the operating ambient temperatures and pressures required in the gaseous-discharge devices, the equilibrium dissociation pressure of the reservoir decreases rather steeply as the absorbed or occluded gas is released and lost to the cleaup process, so that a close approximation to the ideal for supplying additional gas from the reservoir Without varying the pressure in the tube has not been achieved. In addition, relatively small atomic ratios of gas can be occluded for such operating pressures.

An object of the present invention, accordingly, is to provide a new and improved reservoir and method of gas supply of the above-described character that shall not be subject to these disadvantages, but that shall, to the contrary, provide for release of occluded or absorbed gas Without substantial change in pressure for, the required temperatures and pressures, and shall do so while permitting of greatly increased atomic ratios of absorbed gas in the reservoir. In summary, this end is achieved by operating an appropriate reservoir member within a temperature range in which the equilibrium-dissociationpressure, as read from the plateau region of a graph of equilibrium-dissociation-pressure versus atomic ratio of absorbed gas, lies within the required predetermined pressure limits. The term atomic ratio as used herein is intended to mean the number of absorbed gas atoms per atom of metal.

A further object is to provide a new and improved gaseous-discharge device employing such a novel reservoir.

Still another object is to provide a novel gas-supply apparatus of more general utility, as well.

Other and further objects will be explained hereinafter and will be more particularly pointed out in the appended claims.

The invention will now be described in connection with the accompanying drawing Fig. 1 of which is a graph illustrating the before-mentioned equilibrium-dissociationpressure versus atomic ratio of absorbed gas characteristics; and

Fig. 2 is a longitudinal section of a preferred reservoir construction embodied in a gaseous-discharge device.

Referring to Fig. 1, it will be observed that in the preferred 0.1 to 1.0 millimeter pressure-limit range P of, for example, hydrogen rectifiers and thyratrons, such as those described in copending application Serial No. 660,592, filed May 21, 1957, by Seymour Goldberg for Electric-Discharge Device and Cathode, a prior-art titanium reservoir containing absorbed hydrogen gas operates on the initial steeply rising portion I of its equilibrium-dissocation pressure (plotted in millimeters along theordinate) versus atomic ratio of absorbed gas (plotted along the abscissa) characteristic. This characteristic applies for an operating temperature of the reservoir sufiiciently high to minimize the eifects of ambient temperature variations in such gaseous-discharge devices; namely, a reservoir temperature in the neighborhood of 1000 K. The initial portion I is then followed by a horizontal plateau region I, where, as the atomic ratio of absorbed gas varies, substantially no change in equilibrium dissociation pressure occurs. The characteristic .then rapidly rises to the far right. Clearly the plateau region I is the desirable operating portion of the characteristic for the purposes of the present invention. Unfortunately, at the 1000 K. temperature, that plateau I can only be obtained for a high 5.0 millimeters of pressure, entirely outside the required pressure-limits P. Even if the higher pressure were useful, moreover, the plateau only exists for a very limited region of from about .05 to about .25 atomic ratio of absorbed gas, providing very limited reservoir capacity. In the region I, moreover, only a maximum of .025 atomic ratio gas-absorption capacity exists, and, as before state, as gas is released, the pressure drops sharply.

It has been discovered, however, that there are certain materials that, unlike the prior-art titanium, zirconium and similar reservoir materials, can be operated in the required high gaseous-discharge device temperature-range to produce plateau regions in the equilibrium-dissociation-pressure versus atomic ratio of absorbed gas characteristic that lie within the required pressure limits P. More than this, the extent of such plateau regions is very much larger than the extent of the prior-art reservoirmaterial plateaus.

Specifically, in the case of the hydrogen rectifiers, thyratrons and similar gaseous-discharge devices, it has been found that the rare earth materials have the property of providing very long plateau regions within the preferred pressure range P at the 1000 K. temperature. The rare earths include elements number 57 through 71 in the periodic table; namely, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. As shown in Fig. l, the horizontal plateau region for cerium occurs at a pressure of one millimeter at 1000 K. and for a wide range of from less than 0.2 to 1.9 atomic ratio of absorbed hydrogen gas. Similar plateau regions are illustrated for lanthanum and neodymium at the very desirable operating tube pressure of one-half millimeter andI at the. pressure of two tenths of a millimeter, respective y.

The pressure in the plateau region may be altered from these values by raising or lowering the temperature from 1000" K. without appreciably affecting the extent of the plateau region. For the case of cerium a plateau pressure of 0.36 millimeter may be obtained at 971 K. While at 1073 K. a. plateau pressure of about 4 millimeters is had. Further, since all of the rare earths are remarkably similar in chemical behavior, it is to be expected that alloys and combinations of various rare earths would produce results similar to those described above.

The reservoir of the present invention is shown in Fig. 2 embodied in a ceramic-vessel thy ratron-type tube having a cup-shaped anode electrode 1, an inverted cupshaped control electrode 3 and a vane-type cathode electrode 5, as described in the said copending application. These three electrodes are provided with flanges 1, 3', 5' sealed between ceramic-vessel wall sections 2, as more fully set forth in the said application. The control electrode 3 may be apertured as at 7 and disposed close to the anode 1, and a grid bafile 9, overlying the apertures 7 may also be provided. A cathode bafile 11 may also be employed. A fuller description of the tube and further details of its construction are omitted in order not to detract from the novel features of the present invention.

The reservoir 4 comprises a cup 6 containing the hydrogen-gas-saturated rare earth material or materials 6. The upper cover 8 is apertured and covered by a wire mesh screen 10, having a lid 18 attached by a porous Weld thereto, thus providing a gas diifusion outlet for the reservoir. A spiral heater 12, energizable by conductors 14 and 16 (the latter of which communicates with the cathode-cup flange 5' and the former of which may extend outside the base of the tube), will heat the reservoir to the required temperature. The height of the reservoir chamber 6 is intentially made small so that the length of the difiusion path from any point of the chamber is short. The short diffusion path and the proximity of the heater Winding 12 provide improved thermal efiiciency and warmup. A heatretaining baffle 20 may also be employed.

While the invention has been described in connection with a particular type of gaseous-discharge device, it is to be understood that it is also useful with other types of tubes and devices, and, from a more broad point of view, is useful in general as a source of gas that can supply gas Without changing the equilibrium dissociation pressure.

Further modifications will occur to those skilled in the art and all such are considered to fall Within the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A gas reservoir for a closed vessel that is to remain pressurized within predetermined pressure limits, having, incombination, a member comprising a rare-earth or the like containing absorbed gas, and means for operating the member within a range of temperature in which the plateau in the equilibrium-dissociation-pressure versus atomic ratio of absorbed gas characteristic thereof lies within the said predetermined pressure limits and within the atomic ratio range of approximately 0.2 to 1.9.

2. A gas reservoir for a closed vessel that is to remain pressurized within predetermined pressure limits, having, in combination, a member comprising a rare-earth or the like containing absorbed hydrogen gas, and means for operating the member within a range of temperature in which the plateau in the equilibrium-dissociation-pressure versus atomic ratio of absorbed hydrogen gas characteristic thereof lies within the said predetermined pressure limits and within the atomic ratio range of approximately 0.2 to 1.9.

3. A gas reservoir for a closed vessel that is to remain pressurized within predetermined pressure limits of from. substantially one-tenth to substantially one millimeter of pressure, having, in combination, a member comprising a rare earth or the like containing absorbed hydrogen gas, and means for operating the member at a temperature in the neighborhood of substantially one thousand degrees Kelvin whereby the plateau in the equilibrium-dissociation-pressure versus atomic ratio of absorbed hydrogen gas characteristic thereof lies within the said predetermined pressure limits and within the atomic ratio range of approximately 0.2 to 1.9. i

4. A gaseous-discharge device comprising a closed vessel containing a plurality of electrodes and a hydrogen gaseous medium of predetermined pressure, a gas reservoir member within the vessel comprising a rare earth or the like containing absorbed hydrogen gas, and means for operating the member at a temperature at which the plateau in the equilibrium-dissociation-pressure versus atomic ratio of absorbed gas characteristic thereof occurs at substantially the said predetermined pressure and within the atomic ratio range of approximately 0.2 to 1.9.

5. A gaseous-discharge device comprising a closed vessel containing a plurality of electrodes and a gaseous medium of predetermined pressure, a gas reservoir within the vessel comprising a rare earth or the like containing absorbed gas and disposed within a container having a diffusion outlet, and means for heating the reservoir to a temperature at which the plateau in the equilibrium-dissociation-pressure versus atomic ratio of absorbed gas characteristic thereof occurs at substantially the said predetermined pressure and within the atomic ratio range of approximately 0.2 to 1.9.

6. A device'as claimed in claim 4 and in which the predetermined pressure is within the range of from substantially one-tenth to substantially one millimeter of pressure.

7. A device as claimed in claim 6 and in which the said temperature is in the neighborhood of one thousand degrees Kelvin.

8. A device as claimed in claim 5 and in which the difiusion outlet comprises a screened aperture in the con- ,tainer and in which a bafiie is disposed thereabove.

9. A hydrogen discharge device comprising a closed vessel containing at least an anode and a cathode and filled with hydrogen gas of predetermined pressure, a gas reservoir disposed within the vessel on the opposite side of the cathode from the anode and comprising a rare earth or the like containing absorbed hydrogen gas, and means for heating the reservoir at a temperature at which the plateau in the rare-earth equilibrium-dissociation-pressure versus atomic ratio of absorbed gas characteristic occurs at substantially the said predetermined pressure and within the atomic ratio range of approximately 0.2 to 1.9.

10. A hydrogen discharge device comprising a closed vessel containing at least an anode and a cathode and filled with hydrogen gas of predetermined pressure, a gas reservoir disposed within the vessel and comprising a rare earth selected from the group consisting of lanthanum, cerium, praseodymium, neodymium and samarium containing absorbed hydrogen gas, and means for heating the reservoir at a temperature at which the plateau in the rare-earth equilibrium-dissociation-pressure versus atomic ratio of absorbed gas characteristic occurs at substantially the said predetermined pressure and within the atomic ratio range of approximately 0.2 to 1.9.

References Cited in the file of this patent UNITED STATES PATENTS 2,497,911 Reilly et a1. Feb. 21, 1950 2,572,881 Rothstein Oct. 30, 1951 2,766,397 Nienhuis Oct. 9, 1956 2,804,563 Palmer Aug. 27, 1957 

